<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>

    <style>
      li {
        border: solid;
        margin: 10px;
      }
    </style>
  </head>
  <body>
    <ul id="list">
      <li>css</li>
      <li>html</li>
      <li>js</li>
    </ul>
    <script>
      const ul = document.getElementById("list");

      ul.onmouseover = function () {
        this.style.background = "yellow";
      };
      ul.onmouseout = function () {
        this.style.background = "";
      };
    </script>
  </body>
</html>
